Frozen carbonated beverage apparatus and method and control system therefor

ABSTRACT

The present invention concerns improvements in the electronic control of frozen carbonated beverage machines and improvements in electric defrost heaters used therein. A control scheme is shown that provides for accurately determining the viscosity of a semi-frozen beverage as a function of the torque of a drive motor used in the harvesting and mixing thereof. The torque is first calculated based upon the current and voltage to the motor and the phase difference there between. The torque is adjusted to compensate for motor efficiency after which the net torque value is converted to a viscosity scale. The viscosity scale has a zero value relating to the net torque experienced by the motor when the beverage is known to be completely liquid. Viscosity is maintained within a narrow range based upon pre-defined three level low, medium and high viscosity sets, and wherein compressor short-cycling is eliminated. Recalibration control is shown for reestablishing a new viscosity zero value to allow for changes in the net torque at the beverage known liquid point that can result from machine wear, inaccurate initial calibration and the like. A safety defrost control is shown for reducing potential hazards associated with the use of electric defrost heaters. improved electrical defrost heaters are shown that allow for easy removal and replacement thereof.

BACKGROUND

The present application is a continuation-in-part of U.S. Ser. No.07/495,876, filed Mar. 19, 1990.

FIELD OF THE INVENTION

The present invention relates generally to frozen carbonated beveragedispensing equipment, and more particularly to control and defrostingapparatus therefor.

BACKGROUND OF THE INVENTION

Frozen carbonated beverage machines are well known in the art, as seen,for example, in U.S. Pat. Nos. 3,608,779 and 3,460,713 to Richard T.Cornelius. Such equipment is designed to produce a slush beverage fromthe partial freezing of a combination of carbonated water and syrup.This confection is made by the continual harvesting thereof from theinterior perimeter of a refrigerated cylinder.

Originally, frozen carbonated beverage machines were operatedelectro-mechanically. However, it was found that changes in ambientconditions, rate of beverage dispensing and the like, would have a greateffect on the viscosity of the beverage, causing a drink to becomeeither unacceptably loose or firm, as electro-mechanical systems wouldreact too slowly or would overcompensate. Electronic controls are nowused to provide for an improved ability to maintain the beverageviscosity within a predetermined desired range. As is known in the art,electronically pulsed expansion valves can provide for preciserefrigeration control. Also, sensing the torque or power consumption ofthe motors that drive the harvesting mechanism provides an indication ofthe viscosity of the beverage. Thus, viscosity control is exertedthrough the use of electronically pulsed expansion valves operated inaccordance with the sensed harvesting motor torque. However, scrapermotors power requirement during a freezing cycle includes the resistancethat results as the harvesting mechanism removes the portion of thenewly semi-frozen beverage from the cylinder walls, as well as otherfactors normally present. Such factors include the frictional resistancethat results from the mere contact between the harvesting mechanism andthe cylinder interior, the drag caused by the beverage itself and thatresulting from the motors and associated drive train components. Priorart machines have not been able to differentiate well between thesevariables. Thus, for example, during a freezing cycle harvesting loadcan be falsely interpreted to indicate that the beverage held in thecylinder has reached a desired firmness, whereupon refrigeration isstopped by turning off the compressor. However, if the beverage were notsufficiently firm, the sensed load would decrease rapidly as thestopping of refrigeration ends the production of further frozenbeverage, hence the harvesting load associated therewith. Thus,refrigeration can be prematurely terminated, only to be quicklyrestarted, as the F.C.B. i.e. the frozen carbonated beverage machinecontrol was not able to differentiate between the contribution of thetwo load factors. This ineffective control ability results indeleterious short-cycling of the compressor.

A further problem with respect to viscosity control relates to the easeof operation of the F.C.B. machine. Prior art machines inevitablyrequire fine tuning and precise adjustment of the electronic hardwarethereof by trained service personnel. Such adjustments can be frequentand of subtantial cost and inconvenience to the owner/operator who lacksthe skill and knowledge necessary to attempt any direct manipulations ofthe machines electronics. Adjustment can be required due to changes inscraper motor load that can occur over times as the machine is used andvarious moving components, such as the harvesting mechanism, motorcomponents and drive train, wear. Thus, if the load sensed on the motorsdoes not compensate for such changes, the resulting beverage viscositywill also change over time for any given viscosity setting.

Repair of an F.C.B. machine can also be costly due to the amount oftechnician time that can be required to diagnose the particular problem.Thus, it would be very desirable to have an F.C.B. machine wherein thevarious sub-components could be quickly and easily evaluated.

It is also known in the art that the refrigeration components of anF.C.B. machine can be placed in a remote location and connected to thedispensing portion by appropriate refrigeration and water lines. In thismanner the over-the-counter portion utilizes less space in the retailarea. However, a problem with such units having remote refrigerationconcerns the heating and defrosting of the cylinders that isperiodically required for the removal of particulate ice formation inthe beverage, and for maintenance or cleaning of the cylinders. Hot gascan be cycled from the refrigeration system through the evaporator coilsto provide for the defrosting. However, if the lines connecting theremote refrigeration unit to the cylinders are exposed to excessivelycold ambient conditions, the hot gas may not be of sufficienttemperature to provide for adequate defrosting when it reaches theevaporator coils. Thus, electrical heating of the cylinders has beenused. These prior art heaters are generally tubular and lie adjacent andparallel to the cylinders and in direct contact with the evaporatorcoils. The cylinders and heaters are held within a cylinder boxsubstructure, the void areas of which are filled with a foam insulation.If a heater should fail, repair of the cylinder box can be very costlyas such repair necessitates the time consuming steps of removal of thecylinder box from the machine, removal of the insulation, replacement ofthe heater and, finally, re-insulating and replacement of the box in themachine. Therefore, it would be desirable to provide for easilyreplaceable electric heaters in an F.C.B. machine. It would also bedesirable to have an F.C.B. machine that provides for improvedmonitoring and control of electrical defrost heaters to minimize anyhazards associated with the operation thereof.

SUMMARY OF THE INVENTION

The present invention concerns an electronic control having particularprogramming for use in a frozen carbonated beverage machine. The controlincludes a micro-processor connected to various sensing devices andmachine operating systems for exercising control over the consistency ofthe dispensed beverage in response to the sensed information supplied tothe processor. Specifically, harvesting motor power consumption issensed and converted to a displayable viscosity value of a scale runningfrom -9 to 99. The zero value of the scale is established at the end ofeach defrost cycle and represents the cumulative motor load at a pointat which the beverage viscosity is known to zero. The pre-definedviscosity scale is established having several discrete settings whereineach setting has associated therewith a low, medium and high viscositynumber. Each number corresponds proportionately to a sensed powerconsumption of a harvesting motor. Viscosity is controlled by aprogrammed series of steps wherein, after selection of a desiredviscosity value, as represented by a low number, refrigeration iscommenced and semi-frozen beverage is harvested from the cylinder walls.Motor torque is sensed periodically, and when that torque, afternumerical conversion to the corresponding viscosity value, exceeds theviscosity high value, the expansion valves are closed stoppingrefrigeration. At this point however, the compressor continues tooperate. A predetermined period of time is allowed to run subsequent tothe closure of the expansion valves during which motor power, henceviscosity, is sensed. If the viscosity of the beverage goes below themiddle level during the predetermined time period, the valve is openedand refrigeration of the cylinder is restarted. Refrigeration continuesuntil the viscosity again exceeds the high value whereupon the timeperiod is started again. If the viscosity does not go below the middlevalue during the time period, the compressor is also shut off. It can beappreciated that the closing of the valves stops refrigeration duringthe predetermined time period so that semi-frozen beverage production ishalted, whereby the load on the motor will be solely to the viscosity ofthe beverage as the other load variables were factored out when the zerovalue was established.

As stated above, the zero value is determined at the end of each defrostcycle when the beverage is completely liquid. At that time, theharvesting motor torque is sensed, converted to the viscosity scale andthat zero value stored in non-volatile memory means. Thus, the presentinvention provide for recalibration of the viscosity zero value aftereach defrost. Recalibration is necessary to account for any changes thatmay occur due to wear of the harvesting motors and associated drivetrains and harvesting mechanism that can cause inaccuracies in the zerovalue set point. Also, recalibration can correct for any initialcalibration errors that can occur during original set-up of the machine,for the difference efficiency variables that are known to exist betweendrive motors of the same type and manufacture, and for other suchrelated variables. It will be appreciated that as a new viscosity zerovalue is stored in the nonvolatile memory after each defrost it ispossible to use the previous number for comparison with the latest zerovalue. In the present invention, if the latest zero value exceeds apre-determined margin, the new value will be compensated for by anaddition or subtraction of an appropriate value. Thus, the presentinvention can automatically adjust for wear of the various movingelements that occurs over time so that the viscosity of the dispensedbeverage remains the same for a given viscosity setting as the machineages. In addition, the control of the present invention keeps track ofthe totals of all recalibrations and will not permit adjustment outsideof a predetermined range.

The present invention also includes a plurality of touch pad switchesand a display for operator interface with the microprocessor. Theoperator, through use of the touch pad, may select a desired viscosityvalue from a range thereof. The electronic control then regulatesbeverage consistency automatically, as above described, without furtherrequirements of the operator. If a more firm or less firm drink isdesired, the operator through use of the touch pad and display selects ahigher or lower viscosity value number respectively. Thus, the presentinvention greatly simplifies the maintaining of a consistent beverageviscosity in a frozen carbonated beverage machine.

The invention herein also includes a diagnose function wherein the touchpad switches provide for incrementing through and energizing variousmachine sub-components. Thus, for example, a beater motor or expansionvalue can be individually selected and briefly pulsed or energized sothat the operation thereof can be verified.

The present invention also includes electrical tube heaters wherein theheating element of each heater is releasably held within an outertubular sealed housing. If a heating element fails, such an element issimply removed from the outer housing tube. In this manner the cost ofelectric heater replacement is greatly reduced as the cylinder box canremain in the machine and the foam insulation does not have to bedisturbed.

A control scenario is also shown that provides for increased efficiencyof defrost heater operation. As is understood by those of skill,defrosting of the cylinders is periodically necessary, due to the buildup of ice particles. As seen in the prior art, such defrosting istypically done for a preset time period, either automatically accordingto a predetermined frequency, or manually as such particles are viewedand defrosting is deemed necessary. However, a preset time period may beinsufficient in some cases, and overly sufficient in others. Ifinsufficient, the purpose of the defrost is not fully realized. Ifheating is run beyond the point in time that the particulate matter ismelted, excessive energy can be used and potential overheating hazardoussituation could occur. Moreover, it has been found that the voltageprovided to the beverage machine can vary to the extend that theoperation of the heaters can be significantly affected. In particular,the higher the line voltage provided to the machine, the less time isneeded for defrost, as the heaters run at a higher temperature. Thepresent invention therefore includes a safety defrost function wherebythe control monitors the current in each pair of heaters separately andoperates dual relay circuits accordingly to insure the correct currentflow therethrough. The dual relays provide for redundant assurance thatcurrent flow to the heaters can always be terminated. The safety controlalso provides for a message display of an error condition and for anaudible alarm. Also, the defrost control function of the presentinvention monitors the line voltage and sets the defrost heating timeperiod accordingly, and monitors the viscosity of the beverage duringdefrost heating such that when the viscosity substantially equals zerofor a preset period of time, defrost is then ended. In this manner, itcan be appreciated that defrosting is done in accordance with majorvariables of line voltage and actual beverage viscosity so the length ofdefrost can be more accurately controlled.

DESCRIPTION OF THE FIGURES

Further objects, features, and advantages of the present invention willbecome evident in light of the following detailed description, whichdescription refers to the following drawings, wherein:

FIG. 1 shows a perspective view of a frozen carbonated beverage machine.

FIG. 2 shows a enlarged detailed view of the control panel of the frozencarbonated beverage machine.

FIG. 3 is a schematic representation of a refrigeration system for afrozen carbonated beverage machine.

FIG. 4 shows a perspective view of a freeze cylinder box unit.

FIG. 5 is a partially cut-away side view along line 4--4 of FIG. 3.

FIG. 6 shows an end view along line 5--5 of FIG. 3.

FIG. 7 is an enlarged view of an electrical defrost heater of thepresent invention along lines 6--6 of FIG. 4.

FIG. 8 shows a schematic diagram of the major components of a frozencarbonated beverage machine and their fluid inter-connection.

FIGS. 9A-9D show a block diagram of the electrical control system of thepresent invention.

FIG. 10 shows an electrical schematic of the heater safety circuit ofthe present invention.

FIG. 11 shows a flow diagram of the load sensing function of the presentinvention.

FIG. 12 shows a flow diagram of the recalibrating function of thepresent invention.

FIG. 13 shows a flow diagram of the viscosity control of the presentinvention.

FIGS. 14A-14C show a flow diagram of the safety defrost cycle functionof the present invention.

FIGS. 15A-15C show a flow diagram of the display and diagnose control ofthe present invention.

FIGS. 16A-16B show a flow diagram of the overall operation of thecontrol of the present invention.

FIG. 17 shows a diagrammatic representation of the arrangement of FIGS.9A-9 D, 14A-14C, 15A-15C, and 16A-16B.

DETAILED DESCRIPTION

A frozen carbonated beverage (F.C.B) machine, generally designated 10,is seen in perspective view in FIG. 1, and includes an outer housing 11having a front surface 11a. Surface 11a includes a control panel 12,also seen in FIG. 2, having pressure sensitive switches 12a and a lightemitting diode (L.E.D) display 12b. Valves 14 provide for dispensingbeverage from machine 10. In describing the present invention a twocylinder F.C.B. machine is illustrated, although such a machine can havevarious numbers of cylinders.

Referring to FIGS. 3-7, machine 10 includes a cylinder box 16,harvesting assembly drive or beater motors 18a and 18b, for eachcylinder 20a and 20b, and refrigeration means. Box 16 contains the twobeverage cylinders 20a and 20b, and each cylinder includes a scraper orharvesting assembly having a central axial rod 22, scraper blade supportbeater bars 24 and scraper blades 26 pivotally secured to beater bars24.

The refrigeration means includes a compressor 28, reservoir 29, and acondenser 30. Reservoir 29 is connected by a line 31 to electronicallypulsed epansion valves 32a and 32b. Expansion valves 32a and 32b controlthe delivery of refrigerant to coils 33a and 33b respectively. Coils 33aand 33b flow into a common outlet 34 which, in turn, is connected tocompressor 28 by line 35. Both coils 33a and refrigerant temperaturesensors 36a and 36b respectively, secured to each of the inlets 37a and37b thereof. A refrigerant temperature sensor 38 is secured to commonoutlet 34.

As is seen in FIG. 5, evaporator coil 33b encircles cylinder 20b, itbeing understood that coil 33a likewise encircles cylinder 20a. Twopairs of heaters 46a and 46b having stainless steel tube bodies 48 withsealed ends 49, are welded to the individual evaporator coils 33a and33b respectively. It can be seen by referring to FIG. 5, that heaterpairs 46a and 46b are secured to their respective evaporators atpositions thereon approximating five and seven o'clock around theperimeter thereof. Each heater 46a and 46b includes a heating element 50having wires 51 for connection to a source of electrical power. Tubebodies 48 have an inside sized to allow for slideable insertion ofelements 50 therein. In addition, it has been found desirable to platethe surfaces of the tubes 48 with copper to provide for improved heatdispersion. Heaters 46a and 46b extend substantially along the entirelength of evaporators 33a and 33b and terminate with open ends 52exterior of rear plate 54 of clyinder box 16 (see FIGS. 5 and 6). As isknown in the art, after cylinders 20a and 20b, and associated evaporatorcoils 33a and 33b, and heaters 46a and 46b are secured to cylinder boxfront surface plate 55 and rear plate 54, the remaining interior or voidareas of cylinder box 16 are filled with a foam insulation 56.

FIG. 8 shows the basic components of machine 10 in schematic diagramshowing their fluid inter-connections. Machine 10 includes a regulatedpressurized source of carbon dioxide 60, having a carbon dioxidepressure sensor 61 providing a regulated supply of carbon dioxide toeach of syrup tanks 62 and 63, blender bottles 65 and 66, and carbonator68. Syrup reservoir 62 provides syrup to blender bottle 66 along syrupline 70 and syrup reservoir 63 provides syrup to blender bottle 65 alongsyrup line 72. Syrup lines 70 and 72 include syrup sold-out floatswitches 74a and 74b for detecting the presence or absence of syrup andsyrup solenoid valves 75a and 76b for regulating the flow of syrup tobottles 65 and 66. A source of potable water, not shown, provides wateralong line 76 to a carbonator pump 78. Line 76 includes a water pressureindicator 80. Carbonator pump 78 provides a pressurized supply ofpotable water to carbonator 68 through line 82. As is understood in theart, carbonator 68, in turn, provides a source of carbonated water alongline 84 and branches 84a and 84b thereof to blender bottles 65 and 66respectively. Line 84a and 84b have carbonated water solenoid valves 85aand 85b therein for controlling the flow of carbonated water to blenderbottles 65 and 66. Blender bottles 65 and 66 includes beverage levelsensors 86a and 86b respectively, and provide a supply of liquidbeverage along lines 88a and 88b to freezing cylinders 20a and 20b forfreezing therein and ultimate dispensing therefrom by valves 14.

A block diagram of the electronic control of the present invention isseen in FIG. 9, and generally designated numeral 100, and includes twocontrol boards 100a and 100b. It will be understood by those of skillthat the various components or circuits of control 100 are well known inthe art and, therefore, a detailed description of the specificschematics thereof will not be included herein. Line current is broughtin on line to isolation circuit 102 and, in turn, to zero crossingdetection circuit 104. Circuit 102 provides for the necessary and stepdown of voltage from the line voltage of nominally 240 volts AC to thelower voltage required by the components of circuit 100. Circuit 102provides a voltage signal at input 106a to analog-level-conversioncircuit 106. Analog level conversion circuit 106 receives signals atinputs 106b and 106c from each motor 18a and 18b and receives signals atinputs 106d and 106e from inlet temperature sensors 36a and 36b,respectively, and receives signals at input 106f from outlet temperaturesensor 38. The signals from level conversion circuit 106 are sent toinput protection circuit 108 and from there are communicated to theanalog digital converter 110a of microprocesser 110. Zero-crossing orsync circuit 104 is connected directly to processor 110 and providesinformation regarding the phase difference between the voltage at input106a and current at each input 106b and 106c. Microprocessor 110 is ahigh density complementary metal-oxide integrated circuit identified asMC68HC11A1 made by Motorola and includes the on chip capabilities of aneight channel analog-to-digital (A/D) convertor 110a having eight bitsof resoulution, a synchronous serial communications interface 110b, 8Kbytes of read-only memory (ROM), not shown, 512 bytes of electricallyerasable programmable ROM (EEPROM) 110c and 256 bytes of random-accessmemory (RAM) 110d, and is capable of addressing 64K bytes of externalROM.

Control 100 further includes a logic level conversion input protectioncircuit 112 receiving inputs from limit switches 114, user interfaceswitches 12a, dip switches 118, and inputs 120a and 120b, representingsignals from defrost heater pairs 46a and 46b respectively. Circuit 112is connected to digital data selecting circuitry 124 that, as is knownin the art, serves to protect processor 110 and regulate the flow ofinformation thereto. A read-only memory 126 is connected tomicroprocessor 110 and provides additional ROM storage. A real timeclock 128 is connected to processor 110 and includes a battery 130.Processor 110 is also connected to output latching circuitry 132 which,in turn, is connected to output protection/driver circuitry 134. As willbe appreciated by those of skill, output latching circuitry 132 andprotection/driver circuitry 134 provide for safe and efficientconnection to output isolation circuitry 136, display board 12b, outputisolation circuitry 140 of output board 100a and output isolatio circuit142 of output board 100b and audible alarm 135.

Isolation circuit 136 provides for safe connection to the higher voltagecarbonator pump 78 and compressor 28. The connection to compressor isindirect through compressor contactor or relay 144.

Display board 12b, as understood by those of skill, includes inputprotection, and display decoder circuitry, 145a and 145b respectively,connected to an alpha numeric eight digit LED display 145c .

It will be appreciated by those of skill that the boards 100a and 100brelate to the control of various components associated with cylinders20a and 20b and are indentical in that regard. Output isolation circuit140 is connected to a current sensing circuit 146a, which circuit isconnected in series with defrost heaters 46a. Current sensing circuit146a is connected to an isolation circuit 148a for providing the signalto input 120a. Circuit 140 is also connected to current sensing circuit150a which, in turn, is connected to beater motor 18b for sensing thecurrent use thereof. Isolation circuitry 152a is connected to circuit150a so that the beater motor current signal can be safely supplied toinput 106b of analog level conversion circuitry 106. Outputdevice/isolation circuit 140 provides control signals to refrigerationexpansion valve 32a, carbonated water supply valve 85a and syrup valve75a. In board 110b, output isolation circuit 142 is connected to acurrent sensing circuit 146b , which circuit is connected is series withdefrost heaters 46b. Current sensing circuit 146b is connected to anisolation circuit 148b for providing the signal to input 120b. Circuit142 is also connected to current sensing circuit 150b which in turn, isconnected to beater motor 18a for sensing the current use thereof.Isolation circuitry 152b is connected to circuit 150b so that the beatermotor current signal can be safely supplied to input 106c of analogconversion circuitry 106. Output decice/isolat circuit 142 also providescontrol signal to refrigeration expansion valve 32b, carbonated watersupply valve 85b and syrup valve 75b.

Serial port 110b of microprocessor 110 is connected to lines 160 and162, each having respectively input and output protection circuits 163and 164, for providing communications to external equipment, such as apersonal computer. Dip switches 118 provides for alternating betweenvarious pre-programmed messages that are shown, if desired, on display12b. Microprocessor 110 is also connected to a power supply monitoringand reset circuitry 166.

As seen in FIG. 10, a further detailed view of the manner of connectionof heater pair 46a to a 240 VAC power source and to processor 110 isshown. For the purpose of efficiency of description of the presentinvention, the connection of heaters 46a is shown, it being understoodthat the connection of heaters 46b is the same. Heaters 46a areconnected in series to a source of 240 VAC, lines L1 and L2. Currentsensing means 146a is also connected to lines L1 and L2 along with anormally open relay defrost switch 172 and a normally open safetydefrost relay switch 174. Sensor 146a, as previously described, isconnected to processor 110, through isolation circuit 148a, conversioninput protection circuit 112, and selecting circuit 124, and relays 172and 174 are connected to processor 110 through isolation circuit 140,protection circuit 134 and latching circuit 132.

Control 100 provides for the periodic and continuous determining of thebeverage viscosity in cylinders 20a and 20b. As is known in the art,viscosity is determined as a function of the power or torque consumptionexperienced by each motor 18a and 18b individually, wherein anincerasing torque reading indicates an increasingly viscous beverage, asgreater power is required to maintain a constant stirring rate of theharvesting mechanism. Various electro-mechanical and electronicstrategies have been employed to determine the power consumption ortorque experienced by an electric motor. Control 100 employs anelectronic approach in accordance with equation P=E×I×COSINE O, i.e.where power (P) is equal to the product of the voltage (E) times thecurrent (I) times the cosine of the angle (O) of the phase differencebetween the voltage and current. Zero crossing or sync circuit 104provides the phases difference information, and isolation circuit 102includes a voltage detection circuit means, not shown, for determiningvoltage, that signal being provided at input 106a. The current isdetermined from input 106b and 106c from motors 18a and 18bindividually. Thus, processor 110 receives the information necessary fordetermining the power consumption of each motor 18a and 18b separately.Processor 110 is an 8-bit microprocessor; however chips of largercomputational ability, such as 16 or 32 bit microprocessors could alsobe used. An 8-bit processor currently provides for a cost savings,however is disadvantaged by reduced computational speed in compraison tolarger processors. Thus, as is done in the present invention, and as isknown in the art, lock-up tables pf pre-defined information arepreferably used as a means to reduce the computational load on themicroprocessor.

A more thorough knowledge of the manner of viscosity sensing in thepresent invention can be had by reference to FIG. 11, wherein thefunctional programming steps related thereto as shown. As seen therein,after a start point (block 200) power is calculated and monitored bymicroprocessor 110 by first reading the line voltage provided at input106a (block 202) reading the motor current provided by outputs 106band/or 106c, depending upon which beater motor load is being determined(block 204) and determining the phase angle (block 206) as supplied byzero crossing circuit 104. Power is then calculated by processor 110 asthe product of these three variables (block 208).

It will be understood that electrical motors vary as to their efficiencyof converting electrical energy to the kinetic energy of motion, whichin the present invention is the movement of the harvesting mechanism andrelated drive train components. Such efficiency depends upon the linevoltage and the particular type of motor being used. In the presentinvention, motors 18a and 18b are rated at 1/4 horsepower, and are madeby General Electric. The efficiency motor curves therefor are determinedby experimental application of various voltage over the anticipatedvoltage range. The results of such tests provide for efficiency curveinformation which is stored in tabular form within Rom 126. Thus, aftercalculation of the power the table is used to compensate for the motorefficiency based upon the sensed line voltage (block 210). The powervalve is then converted to a "gross" viscosity value (block 212) as pera second table stored in ROM 126 providing the relation between therecalculated power consumption and a corresponding viscosity wholenumber. In a preferred embodiment of the present invention, powerconsumption ranges typically from 100 to 300 watts, and is converted toan arbitrary viscosity scale running fron -9 to 99, with the zero valueof the scale representing the load when the beverage is completelyliquid. Such a viscosity scale provides for a one or two digit wholenumber that is easy to use and easily diplayed. The viscosity number isfurther refined by the auto-calibration function (block 214), describedin greater detail below.

By way of example, if the "gross" or initial power consumption of amotor 18 was calculated to be 200 watts, such figure would then have tobe compensated for. Thus, if the motor were 90% efficient at theparticular sensed voltage, the load value would be reduced to 180 watts,as determined from the data in the motor curve table. The resultantnumber would be converted to the viscosity scale by use of the secondtable, to a viscosity of, for example, 1. If the amount of theauto-calibration were a -1, then the resultant "net" or adjustedviscosity would be 0. As indicated in box 216, the final viscosityreading (block 218) is based upon the average of five previouscalculations.

The present invention provides for recalibrating of the zero viscosityset point for each cylinder 20a and 20b. It can be understood that atthe end of each defrost cycle the beverage is completly liquid and,therefore, provides a point in time at which beverage viscosity is knownto be zero. Thus, the only drag on a harvesting drive motor results fromthe resistance contributed by the motor itself, the friction of theharvesting assembly moving against the beverage cylinder walls, and anyfriction inherent in the drive train means connecting each motor to itscorresponding scraping assmebly. Therefore, changes over time in suchcumulative load above or below the original setting, can be compensatedfor by the recalibration program of the present invention. The manner ofre-referencing a new zero point can be understood by referring to thefunctional flow diagram thereof, as seen in FIG. 12. At the end of adefrost cycle (block 230) the viscosity value of the last defrost cycle(block 232) is obtained. If the difference between the new viscosityvalue and zero exceeds a base calibration window setting, (block 234),calibration is necessary. The overall difference between the old and newviscosity readings is determined in block 236, after which a decision ismade as to the magnitude of the recalibration (block 238). At decisionblock 240 it must be determined whether or not the proposedrecalibration would result in the calibration adjustment exceeding apre-determined range. It can be understood that recalibration should notbe permitted beyond a certain limit, as a very low or high resistancerelative to the original sitting may be indicative of mechanical failurewherein an attempt to recalibrate to such a level could be deleteriousto the machine or create a hazardous situation. In the present inventionthe recalibration range is plus or minus 20 viscosity points from theoriginal set-point. If the proposed adjustment is outside of that rangeno recalibration is done (block 241). If the adjustment is acceptable,the adjustment is made (block 242), and the amount thereof is stored inEEPROM 110c or standby RAM 110d, (block 244). The new zero point is thenestablished (block246). A better understanding of the recalibrationfunction can be had by way of numberical examle, wherein if the originalset point is zero, the recalibration window is 3, and upon subsequentdefrost the viscosity reading is 5, then the difference there betweenexceeds 3 and recalibration should be done. The total difference is, ofcourse 5, and the magnitude of the adjustment can be a set figure, suchas 1, or can be variable over a set range of, for example, up to 5viscosity points. Thus, if the magnitude of change allowable is from 1to 5, and the adjustment value selected is the maximum possible, 5, thenthe adjustment would be minus 5 to reduce the set point again two zero.The amount of change, -5, is stored in EEPROM 110c. At the next defrostcycle, if the viscosity reading is 5, relative to the new set point, thesame procedure follows wherein a -5 change is affected. The adjustmentnumber saved in EEPROM 110c, however is not -5 but the total of alladjustments, in this case -10. This stored adjustment number is thecumulative or running total of the amount of each recalibration done atblock 242. It can now be appreciated that it is the stored adjustmentnumber that is locked at in block 240 whereby the determination is madewhether or not the acceptable calibration range of plus or minus 20 hasbeen exceeded. It will be understood by those of skill, that mayvariations to the recalibration software can be made to tailor operationto a particular set of circumstances. The magnitude of adjustment can beset at a constant small value if conservative adjustments are deemeddesirable. In the present invention, viscosity is controlled inaccordance with a three level system as seen in chart A, below.

                  CHART A                                                         ______________________________________                                        Low             Middle  High                                                  ______________________________________                                         7              12      16                                                     8              14      18                                                     9              16      20                                                    10              18      22                                                    11              20      24                                                    12              22      26                                                    ______________________________________                                    

The low numbers represent the viscosity setting normally displayed andselectable by the operator of machine 10, each setting representing apredetermined set of three viscosity numbers. Thus, if a viscosity of 9is selected, the corresponding middle number would be 16 and the highnumber 20. The manner of the control of the viscosity in a cylinder ofmachine 10, cylinder 20a in this example, can now be understood byreference to FIG. 13, showing the functional flow of the programming ofthe present invention relating to viscosity control. Assumingrefrigeration is off (block 250), processor 110 will be continually andperiodically determining viscosity (block 252), as descirbed above. Ifthe viscosity is below the selected low setting, 9 for example,compressor 28 will be turned on (block 254) and valve 32a will begin tomodulate (block 256), thereby sending refrigerant through coil 33aresulting in the cooling of the beverage in cylinder 20a. Such coolingwill continue as long as the sensed viscosity is below the high settingof 20 in this example (block 258). Once the sensed viscosity equals orexceeds the high number, the modulating of expansion valve 32a will bestopped (block 260), thereby discontinuing the freezing of the beveragewithin cylinder 20a. However, compressor 28 continues to run. Atwenty-second timer commences at the stopping of the modulating of valve32a (block 262). Discontinuing modulating, i.e., closing of normallyclosed valve 32a, terminates the freezing of further beverage. Thus, itcan be understood that the resultant scraping load on motor 18a will bequickly eliminated, wherein any further load value in excess of the zeropoint will be due solely to the viscosity of the beverage. If suchviscosity reading goes below the middle value, 16 in our example, priorto the expiration of the twenty-second time period, expansion valve 32awill again start to modulate causing further refrigeration of cylinder20a (block 264). The twenty-second clock will be reset each time theviscosity goes below the middle value and the refrigeration valve 32a isagain modulated. This loop will continue unless and until the viscositystays above the middle value for the entire twenty-second time period(block 266). If the twenty-second clock expires and the viscosityremains above the middle set value, compressor 28 will then be turnedoff (block 268), stopping refrigeration (block 269). Compressor 28 willbe turned on again and valve 32a modulated once the viscosity is seen togo below the low set point. Valves 32a and 32b are modulated on thebasis of the temperature difference between each inlet 37a and 37b andcommon outlet 34. Thus, sensors 36a, 36b and 38 provide such temperatureinformation to processor 110 so that valves 32a and 32b provide for theproper flow of refrigerant. Various pulse modulating strategies areknown in the prior art. In the present invention, processor 110 samplesthe inlet and outlet temperature difference of each coil 32a and 32bevery ten seconds. The on-time, or length of any pulse, is related tothe temperature difference, wherein the greater the difference, thelonger the valve is held open. Whereas, the expansion valve off-time isset at 0.5 seconds. A representative example of such a relationship isseen in Chart B, below, relating to single cylinder operating whereinthe expansion valve is modulated at a base rate of 62% for a fixedperiod of 30 seconds. Chart C, below, shows such data relating to therefrigeration of both cylinders simultaneously wherein both valves aremodulated at a base rate of 37% for a fixed period of 30 seconds.

                  CHART B                                                         ______________________________________                                        Temperature Difference                                                                        On-Time                                                       Inlet/Outlet    (Miliseconds)                                                                            Percentage On                                      ______________________________________                                        Less than 0     509                                                           1-5             150        23%                                                 6-10           300        37%                                                11-15           600        54%                                                16-20           700        58%                                                ______________________________________                                    

                  CHART C                                                         ______________________________________                                        Temperature Difference                                                                        On-Time                                                       Inlet/Outlet    (Miliseconds)                                                                            Percentage On                                      ______________________________________                                        Less Than 0     255                                                           1-5              50         9                                                  6-10           100        17                                                 11-15           250        33                                                 16-20           300        37                                                 ______________________________________                                    

In this manner, the present invention provides for very accurate controlover the viscosity of the frozen beverage of the use of a particularcontrol scenario wherein the sensed load on a beater motor in excess ofa zero value is due to the degree of viscosity of the beverage alone,the other load components having been factored out. In addition, thethree level system in combination with the control program serves toinsure that the beverage is "truly" at the desired viscosity before thecompressor is turned off, thereby preventing harmful short-cyclingthereof. It will be appreciated by those of skill that the values oftable A are determined upon the basis of the desired degree of controlof the acceptable range of viscosity for the particular setting. Theviscosity range for a particular setting is the difference between thecorresponding low and high numbers. Moreover, it will be understood bythose of skill, that the values of table A and the numerical data of thefirst and second tables relating to efficiency curves and power toviscosity conversion, are highly dependent upon many variables, such asthe particular beater motor used, the size of the freezing cylinders,and the like. Thus, it will be appreciated that such numbers must beexperimentally determined for each particular application.

An understanding of the safety defrost function of the present inventioncan be had by referring to the schematic diagram of FIG. 10 and thefunction flow diagram, as seen in FIG. 14. At block 270, F. C. B.machine 10 is in a particular mode, such as "off", "wash", or "auto". Inany such mode, both relay contacts 172 and 174 are open and the outputof sensor 146a is continually looked at to see if current is present(block 272). If current is present, even though both relays 172 and 174should be open, it is clear by review of FIG. 10, that a dangerous faultcondition exists. Therefore, an "unplug" message is shown in display 12b(block 274) and alarm 143 is sounded continuously (block 276). If nosuch current flow is detected, defrost can be selected manually by useof a specific display switch 12a, therefor, or can be initiatedautomatically based upon a pre-programmed defrost time (block 278). Whenthe defrost cycle is started, refrigeration is first initiated (block280) and viscosity is monitored (block 282), as previously described. Atdecision block (284) the viscosity is monitored to determine whether ornot it has reached whatever the set viscosity is at that time. If theviscosity has not reached the set viscosity, decision block (286)determines whether or not the refrigerant timer has expired. If not, theloop continues wherein viscosity is monitored until, as seen in FIG. 14,either the set viscosity is reached or the refrigeration timer timesout. If the refrigeration timer times out prior to the set viscositybeing reached, 30 minutes in the present invention, a refrigerationerror situation has occurred (block 288) and a beeper is initiated for aperiod of time, for example 15 seconds (block 290) and the machine isreturned to an off, wash or auto mode (block 292). However, if the setviscosity is first reached, the program proceeds to close the defrostrelay 172 (block 294) after which a flow of current is checked by sensor146 (block 296). It can be appreciated by review of FIG. 10 that, ifboth relays 172 and 174 are open, yet current is sensed upon the closingof only relay 172, a potential hazard situation exists. Thus, relay 172is opened (block 298), an error message is displayed (block 300)indicating a relay problem, after which the alarm is sounded for 15seconds (block 302). Machine 10 is returned to the original mode (block292) after completion of defrost timer (block 304). If, after theclosing of defrost relay 172, no current is sensed (block 294), defrostrelay 172 is reopened (block 306), after which safety relay 174 isclosed (block 308). If current is again detected (block 310), safetyrelay 174 is opened (block 312), thus leading to the same error messageand alarm as, again, a hazard situation may exist. Thus, it can be seenthat the control of the present invention provides for independenttesting of each relay 172 and 174. If, after testing of each relay, nounexpected current flow is detected, defrost relay 172 is closed (block314) and defrost heating is started (block 316). Defrost current isagain sensed (block 318) and if such current does not exist, a messagewill be displayed (block 320) indicating a lack of heat or heater error,whereupon alarm 143 will be sounded for a period of time, such as 15seconds (block 302). If current exists at block 318, the line voltage tobeater motors 18 is sensed and a safety timer is set accordingly (blocks322 and 324). Microprocessor 110 includes look-up tables defining thelength of the safety timer setting as correlated with variations thatoften occur in line voltage. It has been found that, as the line voltagesupplied to beverage machine 10 is increased, the length of the defrosttime can be proportionally decreased, due to the higher heat resultingfrom the increased voltage. Those of skill in the art will appreciatethat the particular relationship is variable depending upon heater motorsize, heater wattage, cylinder volume, and so forth. In the presentinvention, four levels are set: the defrost time is 21 minutes at 207volts and below; 19 minutes at 208-229 volts; 16 minutes at 230-250volts; and 14 minutes at voltages greater than or equal to 251 volts.During heating, the viscosity is monitored (block 326). At (block 328),if the viscosity is found to be substantially stable for a pre-set timeperiod, thus indicating complete defrosting and a liquid beverage, thedefrost relay and safety relay are opened (blocks 332 and 334) and themachine is returned to the off, wash or auto mode (block 292). If theviscosity has not been substantially stable for the pre-set time period,7 minutes in the present case, the safety timer is checked forcompletion (block 330). If the safety timer has not expired, the cyclecontinues through blocks 326 and 328, for as long as either the safetytimer has not run out or the viscosity has not been stabilized for thepre-set time period. If the answer is `yes` with respect to either ofdecision blocks (328) and (330), it can be seen that the defrost cycleis either completed or, with respect to the safety timer, should beended, as it can be understood that the safety timer then prevents thedefrost heater from running for too long a period of time.

As is known in the art, touch switches 12a, as specifically listed andnamed in FIG. 9, are used to control the operation of machine 10, suchas to initiate refrigeration, start a defrost cycle and the like. As inalso understood, switches 12a can be use to obtain informationconcerning the current operating status of its various components.Machine 10 includes a display mode wherein such information can beaccessed, and wherein certain functions of the machine can beprogrammed. The present invention also provides for a diagnose functionin addition to a display function. The operation of the display anddiagnose functions can be understood by referring to FIG. 15. At anytime during the operation of machine 10 (block 320), switches 12a areused to enter the display mode (block 322). Thus, various displayfunctions can be selected by incrementing through and individuallyselecting the one of interest. The particular switch or switches usedfor entering the display mode and for incrementing and selecting isarbitrary and well within the skill of the art and, therefore, in theinterest of efficiency of description herein, need not be explained indetail. The display functions are: diagnose (block 324), defrost (block326), time (block 328), sleep (block 330), wake up (block 332),viscosity set (block 334), vicosity read (block 336), sensors (block338) and voltage (block 340). If the particular block 324-340 isselected, then the related message is displayed and the opportunity fora new setting adjustment, or display of an operating status message, isprovided (blocks 342-356). As control 100 includes a clock 128, theselection of the time function permits the setting thereof and thedisplay of the current time. The selection of the sleep and wake-upfunctions permit the setting and display of individual times at which itmay be desirable to have machine 10 automatically turn off andsubsequently to turn on so that refrigeration does not occur duringtimes of predictable inactivity. Selection of the defrost functionpermits the programming and display of times during the day at which theautomatic initiation of a defrost cycle is desired. In the presentembodiment, for example, up to nine different defrost times arepermitted, with a minimum of 2 hours between any two defrosts. Inaddition, the programming of control 100 does not permit thesimultaneous defrosting of both cylinders, so that dispensable beverageis always available from at least one cylinder. The viscosity setfunction allows the selection and display of the particular viscositysetting from 7 to 12, as per Table A herein. The viscosity read functionallows the individual display of the actual viscosity reading of eachcylinder. The sensors function permits the separate display of thetemperatures at both inlets 37a and 37b as indicated by sensors 36a and36b, and of outlet 34 as indicated by sensor 38. Selection of voltagefunction allows the display of the voltage of lines L1 and L2. Aparticular switch 12a is designated to back-up out of the menu moderepresented by block 357 to exit to the original operating mode (block358).

As seen in FIG. 15, selection of the diagnose function (block 324) firstsignals processor 110 to cut power to all the components of machine 10(block 359), followed by the incrementing through sub-functions thereof(block 360) by repeated actuating of a switch 12a and selection of theparticular function (block 376) by the actuating of a further designatedswitch 12a. The sub-functions are: motors (block 362), heaters (block364), syrup (block 366), water (block 368), valves (block 370),compressor (block 372), and pump (block 374). Selection of the motors,heaters, syrup, water or valves functions, allows the individualanalysis of the operation of either motor 18a or 18b, heater pair 46a or46b, syrup solenoids 75a or 75b, carbonated water solenoids 85a or 85b,or expansion valves 32a or 32b. Once a particular component has beenselected, checking the operation thereof is accomplished by thetemporary energizing of each component separately through the briefpushing of a designated switch 12a (block 378). It will be understoodthat each function block 362-370 actually represents a sub-selectionbetween the related component for each cylinder 20a and 20b. Block 380represents the use of a designated switch 12a that allows for backingout of the diagnose or display functions, to the original operatingmodes (blocks 392). It can now be appreciated that the operation ofvarious critical components of machine 10 can be checked initially veryquickly by simply listening for such operation and/or the sounds made bythe energizing of associated relays or solenoids. In addition, thediagnose function can allow for more quantitative analysis of criticalcomponent function through the use of voltage of ohm meters, and thelike.

The overall operational control of machine 10 by the program of thepresent can be had by referring to FIG. 16. As seen therein, machine 10is first powered-up (block 400), after which the initializingprogramming is started (block 402). It is understood by those of skillthat an initialize program provides for a coordinated starting ofmachine 10 by control 100, by resetting the external input/outputcircuitry, clearing all user RAM and the like. After initialization, allinput switches 12a are decoded (block 406), after which the mode flagsare set (block 408). An analog-to-digital conversion function is thenstarted (block 410). Block 410 includes the torque monitoringsub-routine of FIG. 11. A mode monitoring function is commenced at block412, and display 12b is utilized to display the particular mode themachine is in, as determined by decision blocks 416, 418 and 420. Thus,if the defrost function is set (block 416), machine 10 goes into thedefrost mode (block 422), which includes the defrost sub-routine as isdescribed above in conjuction with FIG. 14. In addition, as previouslyexplained, after each defrost cycle, machine 10 is recalibrated (block424) as per the auto-calibration sub-routine of FIG. 12. If the automode has been selected (block 418), machine 10 is refrigerating andproducing frozen beverage (block 426). The automatic mode includes theviscosity monitor sub-routine of FIG. 12. If the wash mode is selected,(block 420), machine 10 goes through the wash mode wherein norefrigeration or heater operation occurs (block 428). If the defrost,automatic, or wash modes are not selected, machine 10 is in the off mode(block 430). Control 100 of machine 10 is always monitoring carbondioxide pressure with sensor 61, water pressure with sensor 80, and forthe presence or lack of syrup with sensors 74a and 74b. If these sensorsindicate deficiencies of carbon dioxide pressure, water pressure or lackof syrup (block 432), a message is displayed indicating such a problem.If no such deficiencies are seen, the blender bottle fill function(block 434) will not be disabled. The bottles 65 and 66 will be allowedto fill in response to level sensors 86a and 86b by operation of valves85a and 86b and 75a and 75b. If, during any mode, a "menu" flag is set(block 436) the display function can be entered (block 438). The displayfunction includes the display/diagnose sub-routine of FIG. 15.

It will be understood serial communication 110b allows for access to allvariables stored in the microprocessor (RAM, EEPROM, etc.). Suchinformation can include the viscosity set-points of cylinders 20a and20b, the cumulative auto-calibration total for each cylinder, the presetautomatic defrost times, and the sleep and awake times.

The present invention has been described herein with reference tovarious preferred embodiments. However, those of skill in the art willrecognize that changes may be made in form and detail to the presentinvention without departing from the spirit and scope thereof.

I claim:
 1. A frozen carbonated beverage machine including:a freezingcontainer for retaining and producing the beverage therein,refrigeration means including a compressor, and an evaporator, theevaporator secured to the exterior of the freezing container forproviding freezing of the beverage retained therein and the evaporatorhaving expansion valve means for regulating the flow of refrigeranttherethrough, harvesting means in the freezing cylinder for harvestingfrozen beverage from the interior surface thereof, a drive motor foroperating the harvesting means, heating means in close association withthe freezing cylinder for providing heating of beverage containedtherein, electronic control means, the control means connected to theheating means and to means for sensing the viscosity of the beverage andthe control providing for the monitoring of the sensed viscosity and foroperating the heating means for defrosting the beverage therein and thecontrol terminating the heating of the cylinder if the sensed viscosityremains stable for a first predetermined period of time.
 2. The machineas defined in claim 1, and the control initiating a second predeterminedperiod of time when initiating the heating of the cylinder andterminating the heating of the cylinder at the end of the second timeperiod if during the second time period the viscosity of the beverage isnot stable for the first time period.
 3. The machine as defined in claim2, and the control means having voltage sensing means for sensing thevoltage of a power supply for operating the machine and the controlmeans sensing the voltage of the power supply prior to each initiatingof defrosting for setting the second time period to a plurality ofvalues depending upon the sensed voltage.
 4. The machine as defined inclaim 1, and the control first providing for the freezing of thebeverage to a predetermined viscosity prior to initiating defrosting. 5.The machine as defined in claim 4, and the control providing for a thirdpredetermined time period commencing at the initiating of freezing, andthe control terminating freezing of the beverage if the sensed viscositydoes not reach the predetermined viscosity level during the third timeperiod.
 6. The machine as defined in claim 1, and the heating means inseries with a first switch and the first switch operated by the controlmeans for closing the first switch when heating is desired forinitiating defrosting, and the control means having current sensingmeans for sensing current flow through the heating means and the controlmeans sensing such current flow prior to initiating to each defrostingand preventing closing of the first switch if current is detected priorto closing of the first switch.
 7. The machine as defined in claim 6,and the heating means in series with the first switch means and a secondswitch means and the second switch means operated by the control meansfor closing the first switch and the second switch means when heating isdesired for initiating defrosting and each time defrosting is to beinitiated the control means checking for current flow with the firstswitch means open and the second switch means closed and subsequentlywith the first switch means closed and the second switch means open andterminating defrosting if current flow is detected with either the firstand second switch means are open.
 8. The machine as defined in claim 7,and the control means checking for current flow when both the first andsecond switch means are closed for initiating defrosting and terminatingdefrosting if no current flow is detected.
 9. A frozen carbonatedbeverage machine including:a freezing container for retaining andproducing the beverage therein, refrigeration means including acompressor, and an evaporator, the evaporator secured to the exterior ofthe freezing container for providing freezing of the beverage retainedtherein and the evaporator having expansion valve means for regulatingthe flow or refrigerant therethrough, harvesting means in the freezingcylinder for harvesting frozen beverage from the interior surfacethereof, a drive motor for operating the harvesting means, heating meansin close association with the freezing cylinder for providing heating ofbeverage contained therein, electronic control means, the control meansconnected to the heating means and to means for sensing the viscosity ofthe beverage and the control providing for the monitoring of the sensedviscosity and the control first providing for the freezing of thebeverage to a predetermined viscosity prior to initiating defrosting andoperating the heating means for defrosting the beverage therein when thepredetermined viscosity is reached and the control terminating theheating of the cylinder if the sensed viscosity remains stable for afirst predetermined period of time.
 10. The machine as defined in claim9, and the control commencing a second predetermined period of time wheninitiating the heating of the cylinder and terminating the heating ofthe cylinder at the end of the second time period if during the secondtime period the viscosity of the beverage is not stable for the firsttime period.
 11. The machine as defined in claim 10, and the controlmeans having voltage sensing means for sensing the voltage of a powersupply for operating the machine and the control means sensing thevoltage of the power supply prior to each initiating of defrosting forsetting the second time period to a plurality of values depending uponthe sensed voltage.
 12. The machine as defined in claim 9, and thecontrol providing for a third predetermined time period commencing atthe initiating of freezing, and the control terminating freezing of thebeverage if the sensed viscosity does not reach the predeterminedviscosity level during the third time period.
 13. The machine as definedin claim 9, and the heating means in series with a first switch and thefirst switch operated by the control means for closing the first switchwhen heating is desired for initiating defrosting, and the control meanshaving current sensing means for sensing current flow through theheating means and the control means sensing such current flow prior toinitiating of each defrosting and preventing closing of the first switchif current is detected prior to closing of the first switch.
 14. Themachine as defined in claim 13, and the heating means in series with thefirst switch means and a second switch means and the second switch meansoperated by the control means for closing the first switch and thesecond switch means when heating is desired for initiating defrostingand each time defrosting is to be initiated the control means checkingfor current flow with the first switch means open and the second switchmeans closed and subsequently with the first switch means closed and thesecond switch means open and terminating defrosting if current flow isdetected with either the first or second switch means are open.
 15. Themachine as defined in claim 14, and the control means checking forcurrent flow when both the first and second switch means are closed forinitiating defrosting and terminating defrosting if no current flow isdetected.
 16. A frozen carbonated beverage machine including:a freezingcontainer for retaining and producing the beverage therein,refrigeration means including a compressor, and an evaporator, theevaporator secured to the exterior of the freezing container forproviding freezing of the beverage retained therein and the evaporatorhaving expansion valve means for regulating the flow of refrigeranttherethrough, harvesting means in the freezing cylinder for harvestingfrozen beverage from the interior surface thereof, a drive motor foroperating the harvesting means, heating means in close association withthe freezing cylinder for providing heating of beverage containedtherein, electronic control means, the control means connected to theheating means and to means for sensing the viscosity of the beverage andthe control providing for the monitoring of the sensed viscosity and thecontrol first providing for the freezing of the beverage to apredetermined viscosity prior to initiating defrosting and operating theheating means for defrosting the beverage therein when the predeterminedviscosity is reached and the control terminating the heating of thecylinder if the sensed viscosity remains stable for a firstpredetermined period of time, and the heating means in series with afirst switch and the first switch operated by the control means forclosing the first switch when heating is desired for initiatingdefrosting, and the control means having current sensing means forsensing current flow through the heating means and the control meanssensing such current flow prior to initiating of each defrosting andpreventing closing of the first switch if current is detected prior toclosing of the first switch.
 17. The machine as defined in claim 16, andthe control commencing a second predetermined period of time wheninitiating the heating of the cylinder and terminating the heating ofthe cylinder at the end of the second time period if during the secondtime period the viscosity of the beverage is not stable for the firsttime period.
 18. The machine as defined in claim 17, and the controlmeans having voltage sensing means for sensing the voltage of a powersupply for operating the machine and the control means sensing thevoltage of the power supply prior to each initiating of defrosting forsetting the second time period to a plurality of values depending uponthe sensed voltage.
 19. The machine as defined in claim 16, and thecontrol providing for a third predetermined time period commencing atthe initiating of freezing, and the control terminating freezing of thebeverage if the sensed viscosity does not reach the predeterminedviscosity level during the third time period.
 20. The machine as definedin claim 16, and the heating means in series with the first switch meansand a second switch means and the second switch means operated by thecontrol means for closing the first switch and the second switch meanswhen heating is desired for initiating defrosting and each timedefrosting is to be initiated the control means checking for currentflow with the first switch means open and the second switch means closedand subsequently with the first switch means closed and the secondswitch means open and terminating defrosting if current flow is detectedwith either the first or second switch means are open.
 21. The machineas defined in claim 20, and the control means checking for current flowwhen both the first and second switch means are closed for initiatingdefrosting and terminating defrosting if no current flow is detected.22. A method for controlling a carbonated beverage machine, the beveragemachine having a freezing container for retaining and producing thebeverage therein, refrigeration means including a compressor, and anevaporator, the evaporator secured to the exterior of the freezingcontainer for providing freezing of the beverage retained therein andthe evaporator having expansion valve means for regulating the flow ofrefrigerant therethrough, harvesting means in the freezing cylinder forharvesting frozen beverage from the interior surface thereof, a drivemotor for operating the harvesting means, heating means in closeassociation with the freezing cylinder for providing heating of beveragecontained therein, the method comprising the steps of:initiatingoperating of the heating means for defrosting the beverage, monitoringthe viscosity of the beverage in the cylinder, terminating the operatingof the heating means if the viscosity of the beverage remains stable fora first predetermined period of time.
 23. The method as defined in claim22, and further including the steps of initiating a second predeterminedperiod of time when initiating the heating of the cylinder andterminating the heating of the cylinder at the end of the second timeperiod if during the second time period the viscosity of the beverage isnot stable for the first time period.
 24. The method as defined in claim22, and further including the step of initiating freezing of thebeverage to a predetermined viscosity prior to initiating defrosting.25. The method as defined in claim 24, and providing for a thirdpredetermined time period commencing at the initiating of freezing, andterminating freezing of the beverage if the sensed viscosity doe notreach the predetermined viscosity level during the third time period.26. The method as defined in claim 22, and the heating means in serieswith a first switch and the first switch closing the first switch whenheating is desired for initiating defrosting, and sensing current flowthrough the heating means prior to initiating of each defrosting andpreventing closing of the first switch if current is detected prior toclosing of the first switch.
 27. The method as defined in claim 26, andthe heating means in series with the first switch means and a secondswitch means and the second switch means and closing the first andsecond switch means when heating is desired for initiating defrostingand each time defrosting is to be initiated checking for current flowwith the first switch means open and the second switch means closed andsubsequently with the first switch means closed and the second switchmeans open and terminating defrosting if current flow is detected wheneither the first or second switch means are open.
 28. The method asdefined in claim 27, and checking for current flow when both the firstand second switch means are closed for initiating defrosting andterminating defrosting if no current flow is detected.
 29. The method asdefined in claim 22, and sensing the voltage of a power supply foroperating the machine and sensing the voltage of the power supply priorto each initiating of defrosting for setting the second time period to aplurality of values depending upon the sensed voltage.